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1.
Lysophosphatidic acid (LPA) is a low-molecular-weight lysophospholipid (LPL), which regulates endothelial cells participating in inflammation processes via interactions with endothelial differentiation gene (Edg) family G protein-coupled receptors. In this study, we attempted to determine which LPA receptors mediate the inflammatory response in human endothelial cells. Introduction of siRNA against LPA 1 significantly suppressed LPA-induced ICAM-1 mRNA, total protein, and cell surface expressions, and subsequent U937 monocyte adhesion to LPA-treated human umbilical endothelial cells (HUVECs). By knock down of LPA 1 and LPA 3 in HUVECs, LPA-enhanced IL-1β mRNA expression was significantly attenuated. Moreover, LPA 1 and LPA 3 siRNA also inhibited LPA-enhanced IL-1-dependent long-term IL-8 and MCP-1 mRNA expression, and subsequent THP-1 cell chemotaxis toward LPA-treated HUVEC-conditioned media. These results suggest that the expression of LPA-induced inflammatory response genes is mediated by LPA 1 and LPA 3. Our findings suggest the possible utilization of LPA 1 or LPA 3 as drug targets to treat severe inflammation. 相似文献
3.
Lysophosphatidic acid (LPA) has been implicated in the pathology of human ovarian cancer. This phospholipid elicits a wide range of cancer cell responses, such as proliferation, trans-differentiation, migration, and invasion, via various G-protein-coupled LPA receptors (LPARs). Here, we explored the cellular signaling pathway via which LPA induces migration of ovarian cancer cells. LPA induced robust phosphorylation of ezrin/radixin/moesin (ERM) proteins, which are membrane-cytoskeleton linkers, in the ovarian cancer cell line OVCAR-3. Among the LPAR subtypes expressed in these cells, LPA 1 and LPA 2, but not LPA 3, induced phosphorylation of ERM proteins at their C-termini. This phosphorylation was dependent on the Gα 12/13/RhoA pathway, but not on the Gα q/Ca 2+/PKC or Gα s/adenylate cyclase/PKA pathway. The activated ERM proteins mediated cytoskeletal reorganization and formation of membrane protrusions in OVCAR-3 cells. Importantly, LPA-induced migration of OVCAR-3 cells was completely abolished not only by gene silencing of LPA1 or LPA2, but also by overexpression of a dominant negative ezrin mutant (ezrin-T567A). Taken together, this study demonstrates that the LPA 1/LPA 2/ERM pathway mediates LPA-induced migration of ovarian cancer cells. These findings may provide a potential therapeutic target to prevent metastatic progression of ovarian cancer. 相似文献
4.
Lysophosphatidic acid (LPA), a potent bioactive lipid found in atherosclerotic lesions, markedly induces smooth muscle cell (SMC) migration, which is an important process in atherogenesis. Therefore, understanding the mechanism of LPA-induced SMC migration is important. Several microarray databases suggest that the matricellular protein Cyr61 is highly induced by LPA. We hypothesized that Cyr61 mediates LPA-induced cell migration. Our data show that LPA induced temporal and spatial expression of Cyr61, which promptly accumulated in the cellular Golgi apparatus and then translocated to the extracellular matrix. Cyr61 antibody blockade and siRNA inhibition both diminished LPA-induced SMC migration, indicating a novel regulatory role of Cyr61. SMCs derived from LPA receptor 1 (LPA 1) knock-out mice lack the ability of Cyr61 induction and cell migration, supporting the concept that LPA 1 is required for Cyr61 expression and migration. By contrast, PPARγ was not found to be involved in LPA-mediated effects. Furthermore, focal adhesion kinase (FAK), a nonreceptor tyrosine kinase important for regulating cell migration, was activated by LPA at a late time frame coinciding with Cyr61 accumulation. Interestingly, knockdown of Cyr61 blocked LPA-induced FAK activation, indicating that an LPA-Cyr61-FAK axis leads to SMC migration. Our results further demonstrate that plasma membrane integrins α6β1 and ανβ3 transduced the LPA-Cyr61 signal toward FAK activation and migration. Taken together, these data reveal that de novo Cyr61 in the extracellular matrix bridges LPA and integrin pathways, which in turn, activate FAK, leading to cell migration. The current study provides new insights into mechanisms underlying cell migration-related disorders, including atherosclerosis, restenosis, and cancers. 相似文献
5.
Lysophosphatidic acid (LPA) is a ligand of multiple G protein–coupled receptors. The LPA 1–3 receptors are members of the endothelial cell differentiation gene (Edg) family. LPA 4/p2y9/GPR23, a member of the purinergic receptor family, and recently identified LPA 5/GPR92 and p2y5 are structurally distant from the canonical Edg LPA receptors. Here we report targeted disruption of lpa4 in mice. Although LPA 4-deficient mice displayed no apparent abnormalities, LPA 4-deficient mouse embryonic fibroblasts (MEFs) were hypersensitive to LPA-induced cell migration. Consistent with negative modulation of the phosphatidylinositol 3 kinase pathway by LPA 4, LPA 4 deficiency potentiated Akt and Rac but decreased Rho activation induced by LPA. Reconstitution of LPA 4 converted LPA 4-negative cells into a less motile phenotype. In support of the biological relevance of these observations, ectopic expression of LPA 4 strongly inhibited migration and invasion of human cancer cells. When coexpressed with LPA 1 in B103 neuroblastoma cells devoid of endogenous LPA receptors, LPA 4 attenuated LPA 1-driven migration and invasion, indicating functional antagonism between the two subtypes of LPA receptors. These results provide genetic and biochemical evidence that LPA 4 is a suppressor of LPA-dependent cell migration and invasion in contrast to the motility-stimulating Edg LPA receptors. 相似文献
7.
Lysophosphatidic acid (LPA) is a bioactive lipid growth factor which is present in high levels in serum and platelets. LPA binds to its specific G-protein-coupled receptors, including LPA 1 to LPA 6, thereby regulating various physiological functions, including cancer growth, angiogenesis, and lymphangiogenesis. Our previous study showed that LPA promotes the expression of the lymphangiogenic factor vascular endothelial growth factor (VEGF)-C in prostate cancer (PCa) cells. Interestingly, LPA has been shown to regulate the expression of calreticulin (CRT), a multifunctional chaperone protein, but the roles of CRT in PCa progression remain unclear. Here we investigated the involvement of CRT in LPA-mediated VEGF-C expression and lymphangiogenesis in PCa. Knockdown of CRT significantly reduced LPA-induced VEGF-C expression in PC-3 cells. Moreover, LPA promoted CRT expression through LPA receptors LPA 1 and LPA 3, reactive oxygen species (ROS) production, and phosphorylation of eukaryotic translation initiation factor 2α (eIF2α). Tumor-xenografted mouse experiments further showed that CRT knockdown suppressed tumor growth and lymphangiogenesis. Notably, clinical evidence indicated that the LPA-producing enzyme autotaxin (ATX) is related to CRT and that CRT level is highly associated with lymphatic vessel density and VEGF-C expression. Interestingly, the pharmacological antagonist of LPA receptors significantly reduced the lymphatic vessel density in tumor and lymph node metastasis in tumor-bearing nude mice. Together, our results demonstrated that CRT is critical in PCa progression through the mediation of LPA-induced VEGF-C expression, implying that targeting the LPA signaling axis is a potential therapeutic strategy for PCa. 相似文献
8.
Lysophosphatidic acid (LPA) signaling via LPA receptors (LPA1 to LPA6) exhibits a variety of malignant properties in cancer cells. Intracellular ATP depletion leads to the development of necrosis and apoptosis. The present study aimed to evaluate the effects of LPA receptor-mediated signaling on the regulation of cancer cell functions associated with ATP reduction. Long-term ethidium bromide (EtBr) treated (MG63-EtBr) cells were established from osteosarcoma MG-63 cells. The intracellular ATP levels of MG63-EtBr cells were significantly lower than that of MG-63 cells. LPAR2, LPAR3, LPAR4 and LPAR6 gene expressions were elevated in MG63-EtBr cells. The cell motile and invasive activities of MG63-EtBr cells were markedly higher than those of MG-63 cells. The cell motile activity of MG-63 cells was increased by LPA4 and LPA6 knockdowns. In cell survival assay, cells were treated with cisplatin (CDDP) every 24 h for 3 days. The cell survival to CDDP of MG63-EtBr cells was lower than that of MG-63 cells. LPA2 knockdown decreased the cell survival to CDDP of MG-63 cells. The cell survival to CDDP of MG-63 cells was inhibited by (2 S)-OMPT (LPA3 agonist). Moreover, the cell survival to CDDP of MG-63 cells was enhanced by LPA4 and LPA6 knockdowns. These results indicate that LPA signaling via LPA receptors is involved in the regulation of cellular functions associated with ATP reduction in MG-63 cells treated with EtBr. 相似文献
10.
TRIP6 ( thyroid receptor- interacting protein 6), also known as ZRP-1 (zyxin-related protein 1), is a member of the zyxin family that has been implicated in cell motility. Previously we have shown that TRIP6 binds to the LPA 2 receptor and associates with several components of focal complexes in an agonist-dependent manner and, thus, enhances lysophosphatidic acid (LPA)-induced cell migration. Here we further report that the function of TRIP6 in LPA signaling is regulated by c-Src-mediated phosphorylation of TRIP6 at the Tyr-55 residue. LPA stimulation induces tyrosine phosphorylation of endogenous TRIP6 in NIH 3T3 cells and c-Src-expressing fibroblasts, which is virtually eliminated in Src-null fibroblasts. Strikingly, both phosphotyrosine-55 and proline-58 residues of TRIP6 are required for Crk binding in vitro and in cells. Mutation of Tyr-55 to Phe does not alter the ability of TRIP6 to localize at focal adhesions or associate with actin. However, it abolishes the association of TRIP6 with Crk and p130 cas in cells and significantly reduces the function of TRIP6 to promote LPA-induced ERK activation. Ultimately, these signaling events control TRIP6 function in promoting LPA-induced morphological changes and cell migration. 相似文献
11.
Lysophosphatidic acid (LPA) mediates a variety of biological functions via the binding of G protein-coupled LPA receptors (LPA receptor-1 (LPA 1) to LPA 6). This study aimed to investigate the roles of LPA 2 and LPA 3 in the modulation of chemoresistance to anticancer drug in lung cancer A549 cells. In cell survival assay, cells were treated with cisplatin (CDDP) every 24 h for 2 days. The cell survival rate to CDDP of A549 cells was significantly elevated by an LPA 2 agonist, GRI-977143. To evaluate the roles of LPA 2-mediated signaling in cell survival during tumor progression, highly migratory (A549-R10) cells were generated from A549 cells. In the presence of GRI-977143, the cell survival rate to CDDP of A549-R10 cells were markedly higher than that of A549 cells, correlating with LPAR2 expression level. Moreover, to assess the effects of long-term anticancer drug treatment on cell survival, the long-term CDDP treated (A549-CDDP) cells were established from A549 cells. The cell survival rate to CDDP of A549-CDDP cells was elevated by GRI-977143. Since LPAR3 expression level was significantly higher in A549-CDDP cells than in A549 cells, we investigated the roles of LPA 3 in the cell survival to CDDP of A549 cells, using an LPA 3 agonist, 1-oleoyl-2-methyl- sn-glycero-3-phosphothionate ((2 S)-OMPT). The cell survival rate to CDDP of A549 cells was significantly reduced by (2 S)-OMPT treatment. In the presence of (2 S)-OMPT, the cell survival rate to CDDP of A549 cells was elevated by LPA 3 knockdown. These results suggest that LPA signaling via LPA 2 and LPA 3 is involved in the regulation of chemoresistance in A549 cells treated with CDDP. 相似文献
13.
Synaptic communication is a dynamic process that is key to the regulation of neuronal excitability and information processing in the brain. To date, however, the molecular signals controlling synaptic dynamics have been poorly understood. Membrane-derived bioactive phospholipids are potential candidates to control short-term tuning of synaptic signaling, a plastic event essential for information processing at both the cellular and neuronal network levels in the brain. Here, we showed that phospholipids affect excitatory and inhibitory neurotransmission by different degrees, loci, and mechanisms of action. Signaling triggered by lysophosphatidic acid (LPA) evoked rapid and reversible depression of excitatory and inhibitory postsynaptic currents. At excitatory synapses, LPA-induced depression depended on LPA 1/G αi/o-protein/phospholipase C/myosin light chain kinase cascade at the presynaptic site. LPA increased myosin light chain phosphorylation, which is known to trigger actomyosin contraction, and reduced the number of synaptic vesicles docked to active zones in excitatory boutons. At inhibitory synapses, postsynaptic LPA signaling led to dephosphorylation, and internalization of the GABA Aγ2 subunit through the LPA 1/G α12/13-protein/RhoA/Rho kinase/calcineurin pathway. However, LPA-induced depression of GABAergic transmission was correlated with an endocytosis-independent reduction of GABA A receptors, possibly by GABA Aγ2 dephosphorylation and subsequent increased lateral diffusion. Furthermore, endogenous LPA signaling, mainly via LPA 1, mediated activity-dependent inhibitory depression in a model of experimental synaptic plasticity. Finally, LPA signaling, most likely restraining the excitatory drive incoming to motoneurons, regulated performance of motor output commands, a basic brain processing task. We propose that lysophospholipids serve as potential local messengers that tune synaptic strength to precedent activity of the neuron. 相似文献
14.
Lysophosphatidic acid (LPA) is a low-molecular-weight lysophospholipid enriched in platelets and mildly oxidized low-density lipoprotein (OxLDL). It is suggested that LPA is involved in atherosclerosis, and our previous studies showed that LPA regulates inflammation in multiple cell types. The main aim of this study was to investigate the effects of LPA on the uptake of OxLDL by mouse J774A.1 macrophages. We observed that LPA upregulated fluorescence-labeled DiI-OxLDL uptake in J774A.1 cells. Meanwhile, expression of the class A scavenger receptor (SR-A), a receptor for modified LDL, was also enhanced. Furthermore, pertussis toxin (PTx) or Ki16425 significantly abolished LPA's effects, indicating that G i and LPA 3 are involved in OxLDL uptake and SR-A expression. Of most importance, the LPA-induced OxLDL uptake could be inhibited when cells were incubated with a functional blocking antibody of SR-A. Our results suggest that LPA-enhanced OxLDL uptake is mediated via LPA 3-G i activation and subsequent SR-A expression. 相似文献
16.
The enhanced migration found in tumor cells is often caused by external stimuli and the sequential participation of cytoskeleton‐related signaling molecules. However, until now, the molecular connection between the lysophosphatidic acid (LPA) receptor and nonmuscle myosin II (NM II) has not been analyzed in detail for LPA‐induced migration. Here, we demonstrate that LPA induces migration by activating the LPA 1 receptor which promotes phosphorylation of the 20 kDa NM II light chain through activation of Rho kinase (ROCK). We show that LPA‐induced migration is insensitive to pertussis toxin (PTX) but does require the LPA 1 receptor as determined by siRNA and receptor antagonists. LPA activates ROCK and also increases GTP‐bound RhoA activity, concomitant with the enhanced membrane recruitment of RhoA. LPA‐induced migration and invasion are attenuated by specific inhibitors including C3 cell‐permeable transferase and Y‐27632. We demonstrate that NM II plays an important role in LPA‐induced migration and invasion by inhibiting its cellular function with blebbistatin and shRNA lentivirus directed against NM II‐A or II‐B. Inhibition or loss of either NM II‐A or NM II‐B in 4T1 cells results in a decrease in migration and invasion. Restoration of the expression of NM II‐A or NM II‐B also rescued LPA‐induced migration. Taken together, these results suggest defined pathways for signaling through the LPA 1 receptor to promote LPA‐mediated NM II activation and subsequent cell migration in 4T1 breast cancer cells. J. Cell. Physiol. 226: 2881–2893, 2011. © 2011 Wiley‐Liss, Inc. 相似文献
17.
BackgroundLysophosphatidic acid (LPA) is a local mediator that exerts its actions through G protein coupled receptors. Knowledge on the regulation of such receptors is scarce to date. Here we show that bidirectional cross-talk exits between LPA 1 and EGF receptors. MethodsC9 cells expressing LPA 1 receptor fussed to the enhanced green fluorescent protein were used. We studied intracellular calcium concentration, Akt/PKB phosphorylation, LPA 1 and EGF receptor phosphorylation. ResultsEGF diminished LPA-mediated intracellular calcium response and induced LPA 1 receptor phosphorylation, which was sensitive to protein kinase C inhibitors. Angiotensin II and LPA induced EGF receptor transactivation as evidenced by Akt/PKB phosphorylation through metalloproteinase-catalyzed membrane shedding of heparin-binding EGF and autocrine/paracrine activation of EGF receptors. This process was found to be of major importance in angiotensin II-induced LPA 1 receptor phosphorylation. Attempts to define a role for EGF receptor transactivation in homologous LPA 1 receptor desensitization and phosphorylation suggested that G protein-coupled receptor kinases are the major players in this process, overshadowing other events. ConclusionsEGF receptors and LPA 1 receptors are engaged in an intense liaison, in that EGF receptors are capable of modulating LPA 1 receptor function through phosphorylation cascades. EGF transactivation plays a dual role: it mediates some LPA actions, and it modulates LPA 1 receptor function in inhibitory fashion. General significanceEGF and LPA receptors coexist in many cell types and play key roles in maintaining the delicate equilibrium that we call health and in the pathogenesis of many diseases. The intense cross-talk described here has important physiological and pathophysiological implications. 相似文献
18.
p2y5 is an orphan G protein-coupled receptor that is closely related to the fourth lysophosphatidic acid (LPA) receptor, LPA 4. Here we report that p2y5 is a novel LPA receptor coupling to the G 13-Rho signaling pathway. “LPA receptor-null” RH7777 and B103 cells exogenously expressing p2y5 showed [ 3H]LPA binding, LPA-induced [ 35S]guanosine 5′-3- O-(thio)triphosphate binding, Rho-dependent alternation of cellular morphology, and G s/13 chimeric protein-mediated cAMP accumulation. LPA-induced contraction of human umbilical vein endothelial cells was suppressed by small interfering RNA knockdown of endogenously expressed p2y5. We also found that 2-acyl-LPA had higher activity to p2y5 than 1-acyl-LPA. A recent study has suggested that p2y5 is an LPA receptor essential for human hair growth. We confirmed that p2y5 is a functional LPA receptor and propose to designate this receptor LPA 6. 相似文献
19.
Lysophosphatidic acid (LPA) mediates diverse cellular responses through the activation of at least six LPA receptors – LPA 1–6, but the interacting proteins and signaling pathways that mediate the specificity of these receptors are largely unknown. We noticed that LPA 1 contains a PDZ binding motif (SVV) identical to that present in two other proteins that interact with the PDZ protein GIPC. GIPC is involved in endocytic trafficking of several receptors including TrkA, VEGFR2, lutropin and dopamine D2 receptors. Here we show that GIPC binds directly to the PDZ binding motif of LPA 1 but not that of other LPA receptors. LPA 1 colocalizes and coimmunoprecipitates with GIPC and its binding partner APPL, an activator of Akt signaling found on APPL signaling endosomes. GIPC depletion by siRNA disturbed trafficking of LPA 1 to EEA1 early endosomes and promoted LPA 1 mediated Akt signaling, cell proliferation, and cell motility. We propose that GIPC binds LPA 1 and promotes its trafficking from APPL-containing signaling endosomes to EEA1 early endosomes and thus attenuates LPA-mediated Akt signaling from APPL endosomes. 相似文献
20.
Lysophosphatidic acid (LPA) is a natural bioactive lipid with growth factor-like functions due to activation of a series of six G protein-coupled receptors (LPA 1–6). LPA receptor type 1 (LPA 1) signaling influences the pathophysiology of many diseases including cancer, obesity, rheumatoid arthritis, as well as lung, liver and kidney fibrosis. Therefore, LPA 1 is an attractive therapeutic target. However, most mammalian cells co-express multiple LPA receptors whose co-activation impairs the validation of target inhibition in patients because of missing LPA receptor-specific biomarkers. LPA 1 is known to induce IL-6 and IL-8 secretion, as also do LPA 2 and LPA 3. In this work, we first determined the LPA induced early-gene expression profile in three unrelated human cancer cell lines expressing different patterns of LPA receptors (PC3: LPA 1,2,3,6; MDA-MB-231: LPA 1,2; MCF-7: LPA 2,6). Among the set of genes upregulated by LPA only in LPA 1-expressing cells, we validated by QPCR and ELISA that upregulation of heparin-binding EGF-like growth factor (HB-EGF) was inhibited by LPA 1–3 antagonists (Ki16425, Debio0719). Upregulation and downregulation of HB-EGF mRNA was confirmed in vitro in human MDA-B02 breast cancer cells stably overexpressing LPA 1 (MDA-B02/LPA 1) and downregulated for LPA 1 (MDA-B02/shLPA 1), respectively. At a clinical level, we quantified the expression of LPA 1 and HB-EGF by QPCR in primary tumors of a cohort of 234 breast cancer patients and found a significantly higher expression of HB-EGF in breast tumors expressing high levels of LPA 1. We also generated human xenograph prostate tumors in mice injected with PC3 cells and found that a five-day treatment with Ki16425 significantly decreased both HB-EGF mRNA expression at the primary tumor site and circulating human HB-EGF concentrations in serum. All together our results demonstrate that HB-EGF is a new and relevant biomarker with potentially high value in quantifying LPA 1 activation state in patients receiving anti-LPA 1 therapies. 相似文献
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